It has been publicly known that synthetic polyamide fiber structures are generally dyed and printed using acid dyes. The printing of polyamide fiber structures using an inkjet system has been disclosed by JP-A-6-57650 and other patents, which have proposed the use of certain acid dyes as ink for such printing.
In the meantime, patents such as JP-B2-2672346 and JP-A-188977 have proposed the use of reactive dyes for dyeing and printing natural or synthetic polyamide fiber structure.
Further in connection with the application of an inkjet system in printing a polyamide fiber structure, JP-A-9-268482 has proposed the use of certain reactive dyes as ink for such printing.
However, such prior art has the great disadvantage of not allowing the use of two or more types of water-soluble dyes in dyeing or printing polyamide fiber structure because of the difference in their affinity for such fiber structure, which results in its uneven color and poor color reproducibility.
In addition, the prior art requires the polyamide fiber structure dyed or printed with water-soluble dyes to be subjected to treatment such as steaming for fixation of the dyes onto the fiber, which involves control of the condition for the fixation such as temperature and time.
However, such fixation condition is extremely difficult to control perfectly on an industrial basis, inevitably undergoing variation.
Such variation in the fixation condition also presents a problem of resulting in uneven color and/or poor color reproducibility of the resultant dyed or printed fiber.
The prior art has also a problem of the dyes applied to a fiber structure to print a design pattern on it bleeding out of the outline of the pattern (hereinafter referred to as xe2x80x9cbleedingxe2x80x9d).
Accordingly, no prior art has yet been disclosed to establish a method of printing a polyamide structure using two or more types of water-soluble dyes to allow the polyamide structure to be printed with no uneven color, high color reproducibility and excellent ink bleeding prevention.
The inventors investigated the causes of the above-mentioned problems involved in printing a polyamide fiber structure with water-soluble dyes such as its uneven color, poor color reproducibility and bleeding. As a result of the investigation, the inventors discovered that these problems are closely associated with the water-soluble dyes"" inorganicity values divided by their respective organicity values (hereinafter referred to as their xe2x80x9cinorganicity/organicity values).
It is therefore an object of the present invention to provide a method of printing a polyamide structure using two or more types of water-soluble dyes to allow the polyamide structure to be printed with no uneven color, high color reproducibility and excellent ink bleeding prevention.
The present invention relates to a method of printing a natural or synthetic polyamide structure such as fiber, fabric or sheet using water-soluble dyes to allow the polyamide structure to be printed with no uneven color, high color reproducibility and excellent ink bleeding prevention, such a method based on an inkjet system and an inkset for use with such a method.
The present invention chiefly consists of a method of printing a polyamide structure using two or more of water-soluble dye with an inorganicity/organicity value of 1 to 7 selected so that the ones with the largest and smallest inorganicity/organicity values show a difference of 2 or below between their two such values.